Urocanic acid

Urocanic acid
Names
	Preferred IUPAC name (2E)-3-(1H-imidazol-4-yl)prop-2-enoic acid
	Other names (E)-3-(1H-imidazol-4-yl)acrylic acid
Identifiers
CAS Number	104-98-3 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30817 ;
ChemSpider	643824 ;
ECHA InfoCard	100.002.963
MeSH	Urocanic+acid
PubChem CID	1178;
CompTox Dashboard (EPA)	DTXSID50859181 DTXSID5041148, DTXSID50859181 ;
	InChI InChI=1S/C6H6N2O2/c9-6(10)2-1-5-3-7-4-8-5/h1-4H,(H,7,8)(H,9,10)/b2-1+ Key: LOIYMIARKYCTBW-OWOJBTEDSA-N ; InChI=1/C6H6N2O2/c9-6(10)2-1-5-3-7-4-8-5/h1-4H,(H,7,8)(H,9,10)/b2-1+ Key: LOIYMIARKYCTBW-OWOJBTEDBA;
	SMILES c1c(nc[nH]1)/C=C/C(=O)O;
Properties
Chemical formula	C6H6N2O2
Molar mass	138.124 g/mol
Melting point	225 °C (437 °F; 498 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Urocanic acid is an intermediate in the catabolism of L-histidine.

Metabolism

It is formed from L-histidine through the action of histidine ammonialyase (also known as histidase or histidinase) by elimination of ammonium.

In the liver, urocanic acid is transformed by urocanate hydratase (or urocanase) to 4-imidazolone-5-propionic acid and subsequently to glutamic acid.

Clinical significance

Inherited deficiency of urocanase leads to elevated levels of urocanic acid in the urine, a condition known as urocanic aciduria.

Function

Urocanic acid was detected in animal sweat and skin where, among other possible functions, it acts as an endogenous sunscreen or photoprotectant against UVB-induced DNA damage. Urocanic acid is found predominantly in the stratum corneum of the skin and it is likely that most of it is derived from filaggrin catabolism (a histidine-rich protein). When exposed to UVB irradiation, trans-urocanic acid is converted in vitro and in vivo to the cis isomer.^[1] The cis form is known to activate regulatory T cells.^[2]

History

Urocanic acid was first isolated in 1874 by the chemist Max Jaffé from the urine of a dog,^[3]^[4]^[5] hence the name (Template:Lang-la = urine, and canis = dog).

References

^ Egawa M, Nomura J, Iwaki H: The evaluation of the amount of cis- and trans-urocanic acid in the stratum corneum by Raman spectroscopy. Photochem. Photobiol. Sci., 2010, 9, 730-733.
^ Schwarz T: Mechanisms of UV-induced immunosuppression. Keio J Med 2005;54(4):165-171.
^ Jaffé, M. (1874). "Concerning a new constituent in the urine of dogs". Ber. Deut. Chem. Ges. 7: 1669–1673.
^ M. Jaffe: Ueber die Urocaninsäure. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 8 (1. 1875), p. 811-813.
^ M. Jaffe: Ueber einen neuen Bestandtheil des Hundeharns. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 7 (2. 1874), p. 1669-1673.

External links

The Online Metabolic and Molecular Bases of Inherited Disease - Chapter 80 - An overview of disorders of histidine metabolism, including urocanic aciduria.

[1] Egawa M, Nomura J, Iwaki H: The evaluation of the amount of cis- and trans-urocanic acid in the stratum corneum by Raman spectroscopy. Photochem. Photobiol. Sci., 2010, 9, 730-733.

[2] Schwarz T: Mechanisms of UV-induced immunosuppression. Keio J Med 2005;54(4):165-171.

[3] Jaffé, M. (1874). "Concerning a new constituent in the urine of dogs". Ber. Deut. Chem. Ges. 7: 1669–1673.

[4] M. Jaffe: Ueber die Urocaninsäure. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 8 (1. 1875), p. 811-813.

[5] M. Jaffe: Ueber einen neuen Bestandtheil des Hundeharns. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 7 (2. 1874), p. 1669-1673.

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